ZnO/PSi nanoparticles thin film for NO2 sensing application prepared by pulsed laser deposition

Zinc oxide nanoparticles (ZnO NPs) were deposited on porous silicon using pulsed laser deposition for nitrogen dioxide detection. A silicon wafer was electrochemically etched to produce a high-porosity surface for depositing ZnO nanoparticles. X-ray diffraction analysis revealed a single crystalline pattern for the Si substrate at a diffraction angle of 28.5 & DEG; and a polycrystalline structure with a hexagonal phase of zinc oxide when the porous silicon was coated with the ZnO NPs. Field emission scanning electron microscopy demonstrated the transformation of single-crystal silicon into a porous structure. It revealed a high porosity surface with uniformly distributed pores of 1 & mu;m diameter, while zinc oxide nanoparticles aggregated on porous silicon to form spherical nanostructures with particle sizes ranging from 23 to 54 nm. Photoluminescence analysis of electrochemically etched silicon showed a strong, broad, single-peak emission at 671 nm, while the zinc oxide-coated porous silicon exhibits emission peaks at 375, 542, 670, and 780 nm. NO2 sensing investigations confirmed the enhanced sensitivity response of ZnO deposited on porous silicon compared to ZnO deposited on the silicon substrate. The developed NO2 sensor displayed maximum selectivity and sensitivity (75.3%) at 100 & DEG;C operating temperature, with response and recovery time of 25 and 35 s, respectively, enhancing by about 2.6 times for the ZnO/PSi compared with the ZnO/Si sensor. The simplicity, low cost, and efficiency of the prepared sensors make them a good candidate for gas sensing applications.